The invention relates to a fiber conveying and depositing device to be connected to a carder, wherein a sliver, downstream of the carder exit, passes through a draw frame comprised of at least two driven roller pairs and then reaches a can coiler, wherein the draw frame has a main drive as well as a regulating drive for the last roller pair.
Such a device is disclosed, for example, in letters patent CH 692 349. The sliver leaving the carder reaches first a draw frame and subsequently a can coiler that places the sliver in the form of loops into the can. The draw frame is configured as a regulating draw frame and arranged immediately on top of the can coiler. In this way, it is possible to keep the distance between the exit of the regulating draw frame and the sliver entry opening of the can coiler at a minimum; according to letters patent CH 692 349, this is underscored as being especially advantageous.
With regard to control technology, the device according to said Swiss letters patent is very complex. The principal problem resides in that the working speed of the carder on the one hand, of the draw frame on the other hand, and finally of the can coiler must be adjusted relative to one another in a suitable way. Speed differences must be compensated or regulated. Moreover, according to the Swiss patent it is proposed to incorporate into the control loop the regulating draw frame as well as the drive motor of the carder. This requires that the individual components must be interconnected with one another with regard to control technology. In practice, one is however often faced with the problem of having to mount a can coiler and an interposed draw frame additionally on an already present carder or to retrofit the carder therewith. In such situations, it is often impossible or possible only with high technical expenditure to intervene in the speed control of the carder in the context of an overall regulation of the system.
U.S. Pat. No. 5,774,940 discloses a device in which, for a preset carding speed, a regulation of the roller pairs of the draw frame as well as a separate regulation of the can coiler drive are carried out. Between the regulating draw frame and the can coiler, the sliver is guided as a freely sagging loop. A level sensor detects the height of the loop, and, based on this signal, a speed adjustment for the regulating draw frame on the one hand and the depositing speed of the can coiler on the other hand are derived by means of a process computer.
In practice, it was found that, in the case of modern carders that operate at high sliver speeds and short-wave regulation of the regulating draw frame, the mechanism of the can coiler is overtaxed in regard to following the short-wave regulation of the regulating draw frame in a sufficiently fast way when controlling the depositing speed of the can coiler by means of, for example, a very rapidly operating servo drive. The reason for this resides in relatively large moved masses of the can coiler that, in the case of a sudden speed adjustments, cause high mechanical forces particularly on the bearing of the rotating head of the can coiler.
It is an object of the invention to provide a fiber conveying and depositing device that operates with simple control-technological means and is to be connected to a carder, wherein the device downstream of the exit of the draw frame enables the adjustment and compensation of the sliver speed without having an effect on the sliver quality.